Apparatus for testing physical properties of materials



Sept. 29; 1931. R. ESNAULT-PELTERIE 1,325,387

APPARATUS FOR TESTING PHYSICAL PROPERTIES OF MATERIALS Filed Dec. 14,1926 A 3 Sheets-Sheet 1 INVENTOR A ito rneys W? R. ESNAULT-PELTERIESept. 29, 1931. APPARATUS FOR TESTING PHYSICAL PROPERTIES OF MATERIALS 3Sheets-Sheet 2 Filed Dec. 14, 1926 INVENTOR Sept. 29, 1931. R.ESNAULT-PELTERIE 1,825,387

APPARATUS FOR TESTING PHYSICAL PROPERTIES 0F MATERIALS Filed Dec. 14,1926 I s Sheets-Sheet s INVENTORI MW By Ati orneys silver sulphide orobtaining a coating by the use of hydrogen sulphide. It is obvious thatany surface coating which is sufficiently thin so as not to materiallyaffect the area of the contact circle between specimens and which is ofsuch a nature as to be affected by pressure whereby to record thecontact areas for subsequent study, will serve the purpose. I have foundin actual practice, however, that silver sulphide is particularlysatisfactory inasmuch as it may be deposited in an extremely thin layerupon the surface of almost any specimen, even one of glass, and furthermore, the coating, when subjected to pressure, is so altered as torender the contact area plainly visible and easy to photograph.

Generally considered, the apparatus comprises a rotatable specimenholder or turret, means at one side of the turret for subjecting aspecimen mounted therein to variable butting pressure from a secondspecimen, a source of radiant energy of short wave length such as theX-ray, adapted to illuminate portions of the specimens close to thecontact area between them whereby to cast a shadow, and means forphotographing the shadow line representing a diameter of the contactarea. The apparatus also is provided with means for making directmicrometer measurements of the contact area recorded on the surface of aspecimen.

If specimens of spherical form are employed, the area of the contactcircle up to, and even beyond the point of the elastic limit 1 of thematerial will be relatively small; and

even though the elastic limit of the material is exceeded, the permanentdeformation in the specimen will be only local and will not in any wayinterfere with the subsequent test of the same specimen over ranges ofpressure below the elastic limit of the material at points only slightlyremoved from the contact area where permanent deformation may haveoccurred.

It will be understood that the determinations of the physical propertiesof materials obtained by the use of this apparatus will be affected bythe shape of the specimens tested, and this must be taken into accountif the materials tested are to be utilized in other shapes. The apparentelastic limit of a small sphere of steel of a certain grade will befound, for example, to be materially higher than the elastic limit ofthe same steel in a fiat block. This is due to the fact that a peculiardistribution of stress is set up when two spheres are pressed together,the pressure over the contact area varying from a maximum at the centerof such area, to zero at the circumference of the contact circle. As aconsequence of this, the material at the point of maximum stress is in asense supported by the surrounding material, the stress in which tapersoff to zero.

I am aware that other methods have been proposed for the accomplishmentof certain of the objects above enumerated. The Hertz methodcontemplates, for example, the determination of the contact area betweena transparent specimen, as, for example, glass or silica, and a secondspecimen which is pressed against the first specimen. A microscope,usually provided with an internal source of light, is so mounted as topermit an examination of the contact area by looking through thetransparent s ecimen. The contact area itself is not visi le but itsdimensions will be outlined by light interference rings which areproduced at a radius removed from the contact area by a distance topermit of a separation of the surfaces of the two specimens sufficientto produce interference effects. By this method the actual contact areais not measured. Furthermore, the method is limited in that it requiresthe use of a transparent specimen, whereas the apparatus according tothe present invention permits equally well of the testing of opaquematerials or materials which are only semitransparent.

Another well known method for testing the hardness of materialscontemplates the dropping of a stylus having a hardened point upon thematerial to be tested, and subsequently measuring the size of theindentation made. This method can never give anything like an absolutedetermination of hardness nor is it applicable to the testing of theelastic limit of materials or the modulus of elasticity. In the firstplace, if the stylus leaves any visible dent in the material tested, theelastic limit of the material must have been exceeded, and it is wellunderstood that an examination of the behavior of materials after theelastic limit has been reached gives very little data that is of valuein determining the behavior of materials under conditions to which theyare normally subjected. The method does not lend itself to the testingof materials at stresses below the elastic limit because it does notprovide means for recording the temporary deformations thus obtained,the moment the stylus leaves the specimen the deformation disappearing.

It has also been proposed to press two specimens together and then tosubject such specimens to the action of an etching fluid. After acertain length of time the fluid is washed away and the pressureremoved. The actual area of contact of the specimens will have beenprotected from the action of the etching fluid and will therefore berendered visible. This method is relatively slow and does not permit ofthe continuous examination of any given specimen over a progressivelyvarying range of conditions.

According to the present invention one specimen is mounted in a memberwhich is slidable, and the other specimen is mounted in a member whichis rotatable and susceptsired force whereby definite butting pres-,

ible ofbeing displaced preferably about a vertical axis threughapproximately 1 89, so

as to: permit of the: microscopic examination mens through the action ofa-- push rod wh-ich is controlled-by a beam.- This beam may be" variablyweighted orsubjeeted to any desu-res between the; specimens may beestablished. Means are also provided 7 for relievingthe specimens of thepressure set up by the beam whereby the one specimen mountedintherctatable member maybe 'carmedto aposition where-it may bedirectlyobserved by themicrometer microscope.- In making a db rectphotographic recordrof the shad'owscast by the. oscillating specimens.the X-i-ray is preferably employed for the reason I that because oftherelativelyshort wave length of suchray', light will pass through the exaggregated diameter ofthe-contact circle ren der-ing: the observationsfar from accurate. With the-X'+ray;the shadow cast. by the specimensshows very-'oloselythe actual diameter of the'contact area.

cally recording the progressive effects of varying.- pressures combinedwith a means siblertoi determine by. visual examination at what point.theielastic limit; of the material hasbecn reached, andlthelreaftcrnofurther tests-*needibemade in the majorityofcases, Whereas if HOIIIQEEDS'fOI directly observ-ing. theeifecttof increasing pressure-werepro-'* vided; numerous photographic recordsmight be made -a=fterutlieelastic limithas been:

passed,- this consuming: considerable time which us generally I quiteunnecessary; I

Itawill he understood that the apparatus 'is not limited to thetesting.of specimens zoif' any special shapdisuchi as spheres; nor is'its" uselimited' t'o the determination 1 of any of the physical propertiesotmaterials hereinbe'fore referred to. The apparatus he-rein .L 7' -11Q). after described will be llIlClGlabOOElb) those flangsupportedinflrecess: 21' and be skilled in'the art to provide a deviceappli cable to awide variety of te'sting purposes.

Further. objects of the invention will be set of-ilhistration. y a

Fig.- M is acentral vertical section of Fig u rel;

Fig. 2is aplan view of the deviceshown in Figs. 1 and 1a. v

Fig.-.3 is a cross-section of the photographic device taken along theline IIIIH of- Fig. 1 hereinafter described.

Fig. 4 is a sectional view of a modified form of it member for carrying;one "of the specimens to be tested.

Fig.5 is an elevation-of Fig. i lookin yon the section plane 5-5'i1r thedirectionoifthe arrows.

Fig. 6 is-a perspective view of the edges member.

Fig. Tdrawn to an enlarged'scale is a crosssection of a photographicfilm--carrierhereina-fter described.

FigY'Ymis further magnified-view correspendingto Fig. 7 and shows thedispositionof the. film in the said carrier.

Fig.8 d awn to anenlarged' scale shew'sa modified formof carrierfor usewith a-photographicplate.- i T r Fig. '9 is sectionalviewshowing an ar--rangement according to the known Hertz method hereinafter described,

Fig. is a ragmentary side elevation ofu the apparatus similarflto Fig. 1but in. addi-- tion shows the attachment of a eain'eralto themicroscope. V p

It is assumed for the purpose 'of the presv i entinventionthatthe-specimen.or' specimens. The provislon' of: means forvphotograph1 to be tested consist of say two steel: balls as shown indotted lines in Figure 1 and in full linesin Figure 1a. These-balls areindicated by the reference numerals 1 and 2,-.the ball' 1 beingpositioned in arecess 3 in a rotatable"; member 4. The 'ballQ is supportedinare cess 5 formed on. the inner: end er plunger- Gguidedby balls 6" toreduce friction and: having a recess 7 in which engages a rod -8.f Therod 8 is formed at its outcrend in such manner as to receive thepressure 01"? ad-znife edge '9 formed on a member 10 on which twofurther: aligned knife edges 1L are provided. These knife edges andthe-member 10.- are more particularly. shown iii-Figure 6; The member 10is provided with flanges 12, 13 which engage in recesses provided in thehead-.14" of a scale beam 15"Wl1ih iSpOSl" tionedbetweenjaws 16 onacover-plate 17; The cover-plate 17 is connected to a casing: 18by boltsand nuts 19. In the interior ofthe casing l8 is a sleeve 20 IZIOVidQCLWitli-H" taneously,- coincidence of thegeometrical axis of thecover plate 17 and thezcasin-g 18,

Roentgen ray or equivalent tube 42.

and the correct distance between the knife edges 11 and ball 1, so thatwhen the ball 2 is pressed against the ball 1 by the addition of desiredweights 28 in scale pan 26 the beam 15 is exactly horizontal. Theforward part of the cover-plate 17 carries a bracket 23 to which issecured an upright 24 and on which is supported by means of knife edgesa beam 25, one end of which carries a counterweight26, the other end ofthe beam being connected by means of two links 27 and knife edges to thescale beam 15 at the centre of gravity of the latter, as shown at 28.The counterweight 26 exactly balances the dead weight of the beam 15.

The hollow casing 18 is supported on'an upright 29 secured to a hollowbase 30 and at the rear of the hollow casing 18 is mounted a microscope81 which can be adjusted vertically by the micrometrical adjusting screw32, longitudinally of its axis by the screw 33 and laterally by themicrometrical screw 84. The member 4 which is rotatable preferablythrough 180 about a vertical axis, is provided with a passage 35 topermit of the introduction of a small red or stiff wire to push the ball1 out of the recess 3 when it is necessary or desired to change the saidball. Disposed before the microscope 31 and half in a part 37 of thecasing 18 and half in the said casing 18 is a tangentially arranged hole38 so as to permit of the passage of light rays artificial or naturaltangentially to the ball when the latter has been carried by therotation of the specimen holder 4 into position before the microscope,as shown in dotted lines in Fig. 1a. 39 is a hole for the insen tion ofa. thin rod to expel the ball 2 when its removal is required. 40 is aremovable pin which prevents rotation of the member 4 and 41 is a handleby means of which the member 4 can be rotated.

The hollow base 30 is adapted to carry a The latter, as will be seenfrom Figure 1 of the drawings, is disposed centrally below the balls 1,2. Between the rotatable member 4 and the hollow casing 18 is a space 43through which the X-rays shine from the Roentgen ray tube 42 onto thecontact area between the two balls 1, 2. Disposed halt in the member 4and half in the casing 18 and centrally above and between the balls 1and 2 is a rod r, 44 slidably mounted in a space 45 in the member 4 andthe casing 18.

to a photographic film 51, Figures 3, 7 and 7a, mounted and suitablyretained in position in a recess 52 formed in the lower end of the filmcarrier 47. 53, 54 are set screws for adjustably securing the rod 44 inthe casing 18. The film carrier 47 is provided with a number of holes55, into any one of which a pin 56 can be inserted through a hole 57 ora hole 58 in the rod 44. By means of the pin 56 the film carrier 47 canbe displaced in either direction and a suitable distance when desired.

The cover-plate 17 is recessed as at 59 and therein is pivoted as at 60a lever 61. The end 62 of the lever 61 is adapted to bear on thecover-plate and on a flange 63 formed on the plunger 6 so that the saidplunger can be moved to the right and pressure taken directly off theball 2 and consequently off the ball 1. In front of the end 62 of thelever 61 is a rod 64 which can be displaced by the lever-end 62 intoengagen'ient with a stop 65 so as to ease or slightly lift the beam 15and thus relieve the pressure from the balls.

In Figures 4 and 5 which show respectively a section and an elevation ofthe modified form of the member 4, the balls in this arrangement areadapted for a friction test. As shown there are the balls 1 and 2 aspreviously and an additional ball 66. The ball 1 in this arrangementsupports a light cross bar or beam 67 carrying knife edges 68, 69, fromwhich are hung scale pans 70, 71. To permit of this arrangement themember 4 is recessed as shown at 7 2, and the cross bar 67 projectsthrough the recess 72 and windows 72 in casing 18 to the exterior of theapparatus.

In order to determine the co-eflicient of friction between specimens adefinite pressure is applied to the balls by loading the beam 15. One orthe other of the scale pans 70, 71. at the ends of the cross bar 67 isthen progressively loaded until there is a rotational movement of thecentral specimen 1 with respect to the two specimens between which it ismounted, this movement being due to the torsional stress set up by theweight on the scale pan acting on the lever arm or" the cross bar 67,the leverage of which is sufficient to produce a relatively high torqueas compared with the frictional resistance to rotation occasioned by thevery small contact surface between the balls.

The co-efiicient of friction may also be determined by a somewhatdifferent method. One of the scale pans on the cross bar 67 may beloaded to produce a definite torsional effect on the ball 1, but aneitect which is insuiticient to cause a movement of the ball. The beam15 which causes the butting pres sure between the balls may then beprogressively relieved of weight until a movement of the cross bar 67occurs.

The provision of two scale pans, one at either end of the cross bar, isto permit the taking 5 of .9 a. :seriessof friction :tests in 1 bathdirections.v 1n.actualzpracticesthe leitt;hand -pan, 'fior example/isifirst iloadeduto iefieet a I .movementxof :thebar. 'ailihisxmovement 5slight,.:beingliniitedi by thesizent thewindow -72 inathe :wall of thecasingzor: firameilS. lllhe iweights arerthen: shifted Ite rthe righthand tpfimfiflchthe cross bar rotatediimthe opposite direction. lRegardless of'wh-ih of the methods-abate "describediis'emplnyed a:determinationnfithe contact area between the specimensslmderthe-conditions corresponding :to .those: at which movement 1 occurs 2underthe-stnesshset 11p. by the leading QILBGDQSSZbWI' 6.71is imade.

This determinatiommay beeithen'hyithe photogr-aphic;methodihereirrbefore described :62! hy' vis nal observatioiro'i thevimpiiessienimatle on ithessnrtaee coating :of one ofithesspecismens.:Knowingitheereaof; contactythegbnt- 1 ting :pr-essurebetweenitlierspe'cimens amdzthe torque of -::the cross bar, athe Icoeefi'zcient of :friction and :rxther zfrictional lproperties: ofmaterials may be determined bytcalcnlaitien. It is "imnecessany- Z3110*imoavw the zmrea {of ithe 1 cont act surface between (the 1specimens-,imorder .to determine ztheccoee'fiicientxxdfa friction 1between specimermthe.contourspdfi'whichidiffer one tfro'mtthe rather,:ahecanse 10f? the fact thatthe:pressurenatwanionsiparts; Qfithfl?contactzarea difiers.svmaterially itherpressnree:hein gsat'zalnltllfi'iQGHlfQlILOIf'KSllChZHJIZQEL sand decreasing :to zerosat: the]outer sedge thereof; The; preblemrdifiers rinrthisrrespect 335rmaterially from the problemi niadetermining athe frictionalcoharacteristics 0f i-specimens which have normally flat contactsurfaces. [In the latter; caseztheupressuazezissubstantially n-niiormover-i the: entirevcontactsarea and this somewhatesizmplifies thecomputation. :As previously qlointe'dnout ihomever Eit yis often'highlydesirable todetermi-nethefphysi- Y cal'properties of specimens whichareishaped so as to contend to fthe .icontact. conditions under whichthe materials rtheredfmz'ill be ssh-jectd,insactualacommercialznse.

Figure 17 rldrawnito an enlarged scale shows" the film: carrier 47, 51iindicatingrthe him which: may-the: ;of the; same lengthiasathe filmccarrier 4:7 and 'tthe zsame Width :mzs if/he recess FBoth. sides 3Z4sand of themecess 52; are "hardened-rand J-ShHJIIJGHGdHSQ that the filmcarrier 47 itself ea nuefieetfthe critting of an ordinary 1:photographic: filmhiinto afihn:ribbonzsuclr asfil. .7 v 1Alternately,andasshewnini'FigniexSrthe .:film 51 showninzFigmiresfl'iandll, mayz'hevre- Y placed byra: glass'platezflwhichiszretainediin position inzarrecess'ld hyithez pressure: ofithe twometallic sides 79, whi'eh::are slightly resilient. In thispartiefilarvarranagement the emulsion is placedionzthe -edgeroftztheplate "as at381 'I'f desired-however;theiglassplate 7 7 maybe positivelyretainedinrtherecess/ZS by any suitablermeans.

Figure 9 shows in section-aform torzuse .in' carrying out the Hertzmethodwherein a ball such 1as21is pressed against a guartzlplate WP.Thebal-l'in this arrangementis retained -in;a member E (Figure9)which-takes the:- placeqofthe member 4 shown in Figurc 2,-.the said!member being actuated by themed- 8; and forming "an extension ofthe-y-slidable plun Two methods of usingthe apparatus wi-l1s7 V 110w bedescribed but it should A be clearly Lund-e-rstoo d that these methodsneed not follow each other in seqnenee, nor need. each method be carriedoutlby the apparatus. It isressentiahihowever, forthepurpose ofcomparr58 ing the; results obtained by the first andsecond methodshereinafter described with that obtained by the Hertzfmethod, which willalso be hereinafter described, that the a-ngula-rly displacea-blemembrane-shouldbeire- 5 moved :ELHCl replaced by :another member,.fitted on the slidableimember 6 so as to give the arangenient showninEigureQ.

Further, when it is desired totest forthe coefficient of friction, the-apparatus should K be modified as shown in Figure 4, and inithat casethe angularly displaeeable member 4 hereinbefore described would bereplacedb y another a member of the construction shown iii-Figure l4. i

:T he first: method of examination according to't-he p-resent inventionand using the arrangement as linrF-iglures 1,-1-a; and ,2, either 'ballor both balls may be coated withesilver a snlphi'de. Assuming,howeveu-that ,one'ball, .100 sayth-eball 1;; has been previouslycoatedrwith silver sulphide, the beam 1:5 is; loadedwith aqdefiniteweight ERG b13130 balls are consequently qpressed together.;Afiter.- asuitable time the pressure-on theballs isreleasedtbyimanipallat- 1105 ing the lever- GL-and the pin 4:0 is. remmied from, themember-4c whic-his rotatedsoeasrt'o permit of the ball being; presentedexactly in [front of the-microscopefil; 'zlheangle (through Which-the111Ifll h isrotated-hby meansyof the handle 4:1 isinthepresentzapparatus exactlyylSO". The billlll; of Figdrefl then comes'i-ntogposition tin front of the -microscope 31-:andthee-area of contacheyidenced by I the crush-ed silver coating -QVBI T115 the Whole of; thesaidarea. of contact. andbetangentially ilhuninated through the :hole-38. can? be examined? through the microscepe 4-31. Ifsodesired, both,balls maybe coated i with silver sulphide and placed in; theaap- 2paratus',oneinthemember-,egandthe other 111 the plunger 6, the-member 4.being thereafter lacked in posit-ion by the pin id-and the balls 1thereafter subjected tto pressure. v After a @suitable time the-pressureonthe balls-1 and .22 is, relieved andv the 1 memberAmarrying the coatedball 1 is-rotated intoga position infront oifithe microscopefil throughwhich the con ,tactrfarea on thetcoated baIlZLmay be-eX- Iamined.

47, the photographic record being afterwards examined by means of amicroscope.

It is often convenient to use a combination of the two methods abovedescribed, a plurality of photographic silhouettes of the diameters ofthe area of contact being made with an occasional visual observationthrough the microscope, whereby it may be determined when the elasticlimit of the ma terial has been reached, because otherwise thephotographic observations might be continued unnecessarily. This wouldbe particularly true in the case of testing new materials, the elasticlimit of which was not known.

It will, of course, be understood that the microscope 31 may be providedin the usual manner as shown in Fig. 10, with a camera attachmentwhereby the magnified image may be photographed, and thus a photographicrecord of the effect of various pressures on the surface coating of thespecimen be made.

The Hertz method consists in testing for the hardness of a material byexamining the interference rings which may be produced under pressure.For this purpose the ball 2 (Figure 9) is directly pressed against thequartz plate 36, the said ball being retained in the member 76. Thelatter, when the beam 15 is weighted, is acted on by the plunger 6 ofwhich the member 76 forms an extension. The applied load forces the ball2 against the plane surface of the quartz plate 36. In this arrangementthe area of contact between the ball and the quartz plate is illuminatedfrom the interior of the microscope 31 which is provided in its interiorwith a small refiexion prism which transmits the light nor mally ontothe area of contact. lVhen the ball and the quartz plate 36 are incontact and under pressure, interference rings will be produced aroundthe contact area because of the refraction and reflexion which occurs inthe space surrounding the actual contact area, in which space for acertain distance outward from the contact area there is an extremelysmall separation between the quartz plate and the ball. Theseinterference rings can be; viewed through the microscope and thus thesize of the contact area determined.

The results obtained by the Hertz methodj odsaccording to the presentinvention may be compared therewith or with each other.

It should be understood that with my silhouette method visible light cannot be used, because interferences take place in the parts where thedistance between the two balls becomes very small, and the shadow of theapparent diameter of contact is much larger than when measured by thesilver coating method. The use of X-rays suppresses this inconvenience,because of their much shorter wave length.

By manipulating the film carrier in its holder 44 a considerable numberof photo balls or silica balls, the said apparatus may be used fortesting specimens of different materlals under different pressure or fortesting the specimens of the same material under different pressureswhether such specimens be transparent or opaque. Further, one of theaforesaid specimens may be a standard specimen and the other specimenmay be a sample of any desired material which it is desired to test.

While certain embodiments and modifications of my invention have beenhereinbefore described, it will be understood that the invention is notlimited thereto but that it may be variously modified and embodiedwithout departing from the spirit of the invention as setforth in thefollowing claims.

What I claim is:

1. An apparatus for use in testing the physical properties of materials,said apparatus comprising butting means for subjecting a specimen topressure, and sensitized recording means adapted to receive and preservea record of at least one of the dimensions of the area of contactbetween said specimen and the said butting means.

2. An apparatus for use in testing the physical properties of materials,said apparatus comprising butting means for subjecting a specimen topressure, and photographic means adapted to record a diameter of thecontact area between said specimen and said butting means.

. 3. An apparatus for use in testing the physical properties ofmaterials, said apparatus comprising butting means for subjecting a maybe considered as a standard and the re-flfispecimen to pressure,sensitized recording sults obtained by the first and second methmeansadapted to receive and preserve a recphysical properties of ratuscomprisinghiitti 1 rat-us 'compri'sn ing a specimen *to pressure,'.means adapted niicroscope, Anion from thehetographic'positionltoiaiposat-ion where termed on the the application:of

' stamps? 0rd of at least one i of the dimensions of a the "area orcontaot=between "saidxspecinien and the said butting means, andVlSLtfilJlliQIOEDGC- IlC' means for' measuring the diameter er thecontact aI'GaWIlZhOL'llJ removing the specimen from the apparatus.

4. An apparatus for use instestin'g: the phps real properties :of. materals, said apparatus comprising butting iineains for =sub3ect1ng1 aspecimen to pressure, photographic means adapted to record thesilhouette of the'contie diameter of said contact iarea.

5; An apPHTfltUS torusedntiestingthe aterials, said appameans? forsnbje'cting 1 a specimen ito pressure,

photographic means a dapt'e'd tor-recorder, lnouette of'tiie Contactarea, an'dia source =01 X rayswhereby 1H0 ans.

6. An apparatus for use "in testing the physical propertiesofanaterials, ald appa- "ibutting nieansifor su bgectto"recordthephotographic :iinzrgehf a plane passing through the center :of thecontact area :of the specimen, said; plane. being ssubvstantiallyparallel to direction on the batting rrcssure, sad. specimen havinga-surfacc coating which isfa tf'c'cted by the pressure so as to recordthe contactisarea directly en the sui'i ac'e otthe spec-iinen, la:'crometer lmeans'ltor moving-said speciie record if Y its contact :areacid surface oo-atin' rnmayihc measured rhy' s micrometer microscope.

:7. The stepsinaanethoid ot testinig' the physical? prepare sof?materials comprising the specimen to he tested, such coatinghei-ngthrough a butting member, the mutual: area of contact ihetWo-cnth'exsaid. specimen and mcn'iher being a function of the appliedpressure, and the said coating over the mutual contact area beingaltered. by such pressure so as to optically differentiate such areafrom the rounding surface of the specimen, and subjecting said specimento a determined butting pressure such that upon the releaseof thespecimen, the dimensions of the butting contact area will be recorded inthe surface coating even though the pressure applied during the test heinsutficient to produce a permanent deformation of the specimen.

8. An apparatus for use in testing the physical properties of materials,said appaatus comprising butting means for subjectthin surface ooatingtovAnwapparatmis tor nse Bin testing tlae i physical properties ofmaterials comprising a movahlespecimen holder, means aidaptedi tosuh3e'ct a 813661111611 in said iholderito aaudefi- :nite bnttingpressure, 311111 a micrometer mi- N able specimen holder so thatthespecismen nia "=he='n1oved into the field of the microscope'after theremoval ofthe pressure.

10; An apparatus foruuse intestingthe ore-scope positioned with respectto said himproperties of materials s-ai d a- Jaratus emprising-meansadapted: to receive: two pieces -mater-ial, 'means adapted to press saidpieces of inaterial together, sai d pieces of -1 ,aterial having Icliiierent contours such that "ohanges in their contact pressure result 1in m) changes in their contact area, a and i optical means forascertaininga ldaameter for the contact area While said two 1918088ofmatcrial are pressed together.

11, An apparatus for use inf testing the a physical: properties of-materials, said apparatus including means for su bjectingltwo :er13110i619l6369s0fi materials to a definite vbutting pressure and meansfor photographically recordin the size oh the oonta'ct area existiinbetween said pieces of -ma-teria'l While said pieces are subjectedtotheisaidpressure. v

12. l An 1 apparatus 1 for use in testizng'i the "physical 2 propertiesof materials, said sup- 'lparatusi -or mo re' pieces of materials :to adefinite butting pressure,iai'photmsensitive recording surface, and asource of radiation having photograplliic 1 properties, :said iradiation ingdirected toward the l pieces of: material at right anglesto the line of pressure and i n-a direction-to cast a shadow of thecontasting pieces upon said photosensitive sur face. i l

1T3.IAn ap paratuswaccording1tohclaim 12, further characterized in thatthe-isai'dsphotosensitive irecordin'g rsur-face ficomprises aphotographic 1 filin, a carrier in which said 'ifi-hn isv mounted, andahousing for said carrier disposed: transversely rot? the aap paratus,said carrier being: slidable in' sfidihOusiHg f to bring successiveportions ofsaid: film into reposition! for recordingsuccessive exposuresof: the contact *area between saidr pieces wot material, under different1 pressures.

is. An apparatus accond isngito' clwim 12, further characterized in thatslirdahle car- 1 rier isprovided i101 said photosensitive rccoiidin'gsurface, 'an'dia light; tight housing "for said carrierimithin whichtheisa iid "carrier slides, the said housing being adapted to receivecarriers in which va'ious forms of photo-sensitive records may bemounted.

15. An apparatus for use in testing the physical properties ofmaterials, said apparatus including means for subjecting two or morepieces of material to pressure, a turret in Which one of said pieces ismounted, a microscope for examining the contact area of the piece ofmaterial mounted in said turret, the said turret being rotatable tobring the said piece of material from the position in which it issubjected to pressure to a position within the field of the microscope,and said turretbeing removable from the apparatus.

16. An apparatus for use in testing the physical properties ofmaterials, said apparatus including a slidable member a rotatableturret, a specimen mounted in said turret, said slidable member beingadapted to apply pressure to the said specimen when the turret is in oneposition,'means for obtaining a photographic image of the specimen insaid position and while subjected to pressure, and a micrometermicroscope, the said turret being adapted to swing the specimen from theposition in which it receives pressure to a position within the field ofthe microscope.

17. An apparatus for use in testing the physical properties ofmaterials, said apparatus including a frame, a plunger slidably carriedby said frame and adapted to exert pressure upon a specimen, a beam,oppositelydisposed knife edges toward one end of said beam, one of saidknife edges exerting a thrust upon said plunger, the other of said knifeedges being supported by said frame, and means for recording the area ofcontact between said specimen and a piece of material pressed againstit.

18. An apparatus according to claim 17, further characterized in thatthe beam is horizontal and the knife edges thereon are arrangedvertically one above the other, the upper knife edge bearing against theframe andthe lower knife edge exerting a thrust against the plunger.

19. An apparatus according to claim 17, further characterized in thatthe frame is formed in sections, one of said sections supporting thespecimen, another section supporting the beam, a spring interposedbetween said sections tending to thrust the sections apart, and aplurality of adjustable screw means adapted to bring said parts to thedesired relative adjustment whereby the sections of the frame may beaccurately positioned and all looseness or play between the sectionseliminated.

20. An apparatus according to claim 17, further characterized in thatthe said knife edges are formed integrally in a block, which block isseparate from the said beam but is ri idly mounted toward one endthereof in suc manner as to form virtually a part of the beam.

21. An apparatus according to claim 17, further characterized in thatthe said knife edges are formed so that a central knife edge is flankedon either side by another knife edge, the two flanking knife edgeshaving a common line, which line is parallel to, but removed from theline of the central knife edge.

22. An apparatus according to claim 17, further characterized in thatthe said knife edges are formed on the same member, the knife edgesbeing disposed in substantially a vertical plane, the upper knife edgeshaving a common line of action and flanking the lower knife edge, thesaid upper knife edges engaging the frame of the apparatus and the lowerknife edge engaging the plunger, whereby a load placed at the free endof the beam will be transmitted through a bell crank of high leverage toproduce a relatively large thrust on the plunger.

23. An apparatus for testing the frictional characteristics of specimensof material, comprising means for subjecting specimens to a buttingpressure, a weighted arm connected to one of said specimens tending toovercome the frictional resistance due to the" said butting pressure,and to rotate said specimen, and means for recording the contact areabetween said specimen and another piece of material pressed against itunder the conditions at which rotation occurs.

24. A method of testing the physical properties of materials, saidmethod consisting in v ROBERT ESNAULT-PELTERIE.

